The present invention relates to a molding material and crosslinkable molding composition which comprise a fluorine-containing multi-segment polymer and used suitably for molding of various molded articles demanded to have a sealing property and cleanliness, and relates to various molded articles produced therefrom by molding, particularly a sealing material and semiconductor-related production apparatuses provided with the sealing material.
Fluorine-containing elastomers have excellent heat resistance, oil resistance, chemical resistance, etc. and are widely used in various fields, for example, in the fields of electrical and electronic industries, transportation, chemical industries, machinery, foods and metals as molding materials for a sealing material, O-ring, gasket, oil seal, diaphragm, hose, roll, belt, packing and the like.
For example, in the field of production of semiconductors, contamination in a production process is required to be eliminated as much as possible, and there was proposed an attempt to inhibit elution of metal and enhance a strength by adding a fluorine-containing resin fine powder to a fluorine-containing elastomer comprising fluoroolefin and perfluoro(alkyl vinyl ether) (WO97/08239). However since a fluorine-containing resin fine powder is simply kneaded physically, a fluorine-containing resin is released during use, which causes particles as a foreign matter, lowers gas impermeability and results in insufficient cleanliness and sealing property.
Also a fluorine-containing multi-segment polymer prepared by block-copolymerizing an elastomeric fluorine-containing polymer chain segment with a non-elastomeric fluorine-containing polymer chain segment is known.
JP-A-7-316246 discloses various combinations of components (monomers) constituting a fluorine-containing multi-segment polymer. However a concrete example disclosed therein is only a fluorine-containing multi-segment polymer prepared by block-copolymerizing an elastomeric fluorine-containing polymer chain segment comprising vinylidene fluoride (VdF)/hexafluoropropylene (HFP)/tetrafluoroethylene (TFE) with a non-elastomeric fluorine-containing polymer chain segment comprising polyvinylidene fluoride (PVdF).
JP-A-6-220143 discloses various combinations of components (monomers) constituting a fluorine-containing multi-segment polymer. However concrete examples disclosed therein are only combinations of TFE/propylene, TFE/propylene/VdF and TFE/hydrocarbon type olefin of C2 or C3/perfluoro(alkyl vinyl ether) (PAVE) as an elastomeric fluorine-containing polymer chain segment and PTFE, TFE/ethylene and TFE/PAVE as a non-elastomeric fluorine-containing polymer chain segment.
However those fluorine-containing multi-segment polymers are low in a blocking ratio and contain many polymer molecules comprising only elastomeric fluorine-containing polymer chain segment, to which a non-elastomeric component is not bonded. Therefore in various molded articles produced by molding them, elution of elastomeric fluorine-containing polymer chain segment and other low molecular weight substances occurs and thus heat resistance, chemical resistance and mechanical properties are insufficient. Particularly in case of use as a sealing material for semi-conductor device production apparatuses, in which cleanliness is demanded, there arises a problem with elution of elastomeric fluorine-containing polymer chain segment and other low molecular weight substances due to a low blocking ratio. Also the polymer itself is colored milky white, and transparency which is a characteristic of a fluorine-containing multi-segment polymer is deteriorated.
An object of the present invention is to provide the material for molding, i.e. the molding material and crosslinkable molding composition which comprise a fluorine-containing multi-segment polymer having an elastomeric fluorine-containing polymer chain segment and a non-elastomeric fluorine-containing polymer chain segment, particularly a sealing material for semiconductor-related production apparatuses which is produced by molding the molding material and crosslinkable molding composition and ensures less elution of elastomeric fluorine-containing polymer chain segment and other low molecular weight substances, and semiconductor production apparatuses provided with the sealing material.
The present invention relates to the molding material comprising a fluorine-containing multi-segment polymer having an elastomeric fluorine-containing polymer chain segment (hereinafter referred to as xe2x80x9celastomeric segment Axe2x80x9d) and a non-elastomeric fluorine-containing polymer chain segment (hereinafter referred to as xe2x80x9cnon-elastomeric segment Bxe2x80x9d), in which the elastomeric segment A imparts flexibility to the whole polymer and has perhaloolefin units as a recurring unit.
The molding material of the present invention contains perhaloolefin units as a recurring unit of the elastomeric segment A in an amount of not less than 90% by mole, preferably not less than 95% by mole.
In the present invention, the elastomeric segment A and/or the non-elastomeric segment B may contain recurring units derived from monomer giving a curing site to the respective segments in an amount of not more than 5% by mole based on each segment.
Also it is preferable that the elastomeric segment A is a non-crystalline segment and its glass transition temperature is not more than 25xc2x0 C. and further that the segment A comprises tetrafluoroethylene (TFE)/perfluoro(alkyl vinyl ether) (PAVE)/monomer giving a curing site in an amount of 45 to 90/10 to 50/0 to 5% by mole.
It is preferable that the non-elastomeric segment B is a polymer chain having a crystalline melting point of not less than 150xc2x0 C. and has perhaloolefin units as a recurring unit. Further it is preferable that the non-elastomeric segment B is a non-elastomeric segment comprising 85 to 100% by mole of TFE and 0 to 15% by mole of CF2xe2x95x90CFxe2x80x94Rf1, in which Rf1 is CF3 or ORf2 (Rf2 is a perfluoroalkyl group having 1 to 5 carbon atoms).
The non-elastomeric segment B has at least one fluoroolefin unit and can be used preferably even if it has a haloolefin unit having hydrogen atom as a recurring unit as case demands.
In the molding material of the present invention, it is preferable that the fluorine-containing multi-segment polymer (for example, B-A-B, A-B, etc.) does not contain a polymer molecule C consisting of the elastomeric segment A which is not bonded to the non-elastomeric segment B or even if such a polymer molecule C is contained, its amount is not more than 35% by weight, particularly not more than 10% by weight, in other words, A/(A+C)xe2x89xa765% by weight, particularly A/(A+C)xe2x89xa790% by weight.
The present invention also relates to the crosslinkable molding composition comprising 100 parts by weight (hereinafter referred to as xe2x80x9cpartxe2x80x9d) of the above-mentioned fluorine-containing multi-segment polymer having a curing site, 0.05 to 10 parts of an organic peroxide and 10 to 010 parts of a crosslinking aid.
Also the present invention relates to the crosslinkable molding composition comprising 100 parts of the above-mentioned fluorine-containing multi-segment polymer having a nitrile group as a curing site and 0.1 to 10 parts of a crosslinking agent having a functional group capable of reacting with the nitrile group.
The molding material and crosslinkable molding composition of the present invention can be used for various molded articles, and since contamination is hardly caused, they are particularly suitable as a sealing material for various production apparatuses in the semiconductor-related field.
Also it is preferable that the above-mentioned fluorine-containing multi-segment polymer is used as a sealing material after subjected to crosslinking by high energy rays.
Down-sizing of such a sealing material has advanced more and more and cleanliness thereof is demanded. Concretely a sealing material is built in semi-conductor production apparatuses, for example, etching system, cleaning equipment, exposure system, polishing device, deposition system and diffusion/ion-implantation system.
The molding material of the present invention comprises the fluorine-containing multi-segment polymer which is a block copolymer of the elastomeric segment A and the non-elastomeric segment B and has flexibility, in which the elastomeric segment A has perhaloolefin units as a recurring unit.
The present inventors have found that in the process for preparing a fluorine-containing multi-segment polymer which was referred to in JP-B-58-4728, etc., and disclosed in Kobunshi Ronbunshu (Vol. 49, No. 10, 1992), namely a so-called iodine transfer polymerization process, when not less than 90% by mole, particularly not less than 95% by mole of perhaloolefin units are contained as a recurring unit in the elastomeric segment A, a block copolymerization reaction with monomer for the non-elastomeric segment B advances regularly and uniformly and it is possible to largely decrease an amount of unintended products such as un-reacted elastomeric segment A and the non-elastomeric segment B having a low molecular weight even if a reaction occurs, and further that molded articles produced therefrom are useful as a sealing material for semiconductor-related production apparatuses. On the other hand, molding materials comprising a fluorine-containing multi-segment polymer containing unintended un-reacted elastomeric segment A, etc. have adverse effect on molded articles produced therefrom, such as lowering of mechanical strength, heat resistance, chemical resistance and cleanliness due to elution of impurities.
Examples of the usable perhaloolefin as a recurring unit of he elastomeric segment A are, for instance, TFE, chlorotrifluoroethylene (CTFE), perfluorovinylethers such as perfluoro(alkyl vinyl ether) (alkyl group has 1 to 5 carbon atoms) and
CF2xe2x95x90CFO(CF2CFYO)pxe2x80x94(CF2CF2CF2O)qxe2x80x94Rf
wherein Y is F or CF3, Rf is a perfluoroalkyl group having 1 to 5 carbon atoms, p is 0 or an integer of 1 to 5, q is 0 or an integer of 1 to 5, provided that p+qxe2x89xa71, hexafluoropropylene (HFP), and the like. Among them, those having a combination and composition giving elastomeric property can be used. Further a monomer giving a curing site for peroxide crosslinking, polyol crosslinking, polyamine crosslinking and crosslinking by employing a compound such as bisaminophenol as a crosslinking agent may be introduced in an amount of not more than 5% by mole, preferably not more than 2% by mole, more preferably not more than 1% by mole, and thereby the segment A exhibits better compression set.
In the fluorine-containing multi-segment polymer used in the present invention , the elastomeric segment A is a segment being non-crystalline and having a glass transition temperature of not more than 25xc2x0 C. Examples of preferable composition thereof are, for instance, TFE/PAVE/monomer giving a curing site (45 to 90/10 to 50/0 to 5 in % by mole, hereinafter the same), more preferably 45 to 80/20 to 50/0 to 5, particularly 53 to 70/30 to 45/0 to 2.
Examples of the monomer giving a curing site are, for instance, vinylidene fluoride, iodine-containing monomers represented by CX2xe2x95x90CXxe2x80x94CXxe2x80x94Rf3CHRI, in which X is H, F or CH3, Rf3 is a fluoroalkylene group, perfluoroalkylene group, fluoropolyoxyalkylene group or perfluoropolyoxyalkylene group, R is H or CH3, nitrile-containing monomers represented by 
in which m is 0 or an integer of 1 to 5, n is an integer of 1 to 3, 
in which n is 0 or an integer of 1 to 4,
CF2xe2x95x90CFO"Parenopenst"xe2x80x94F2)nCN
in which n is an integer of 1 to 4,
CF2xe2x95x90CFO(CF2)nOCF(CF3)CN
in which n is an integer of 2 to 5, 
in which n is an integer of 1 to 6,
CF2xe2x95x90CF(OCF2CF(CF3))nOCF2CF(CF3)CN
in which n is 1 or 2, or 
bromine-containing monomers, and the like. Usually iodine-containing monomers and nitrile-containing monomers are suitable.
As the iodine-containing monomer, a perfluoro(vinyl ether) compound is suitable from the viewpoint of copolymerizability. For example, perfluoro(6,6-dihydro-6-iodo-3-oxa- 1 -hexene) and perfluoro(5-iodo-3-oxa- 1-pentene) are suitable.
In addition, there is fluorovinylether disclosed in JP-B-5-63482 and represented by the formula:
ICH2CF2CF2(OCFYCF2"Parenclosest"nOCFxe2x95x90CF2
in which Y is a trifluoromethyl group, n is 0, 1 or 2.
Further there can be used olefin iodide disclosed in JP-A-7-316246 and represented by the formula:
CX2xe2x95x90CXxe2x80x94Rfxe2x80x94CHRxe2x80x94I
in which X is hydrogen atom, fluorine atom or methyl, R is hydrogen or methyl, Rf is a linear or branched fluoro- or perfluoro-alkylene group or fluoro- or perfluoro-oxyalkylene group which may have at least one ether type oxygen atom. In addition, CF2xe2x95x90CHI can also be used suitably.
When vulcanization (crosslinking) is carried out by using high energy rays such as radiation (xcex1-, xcex2-, xcex3- or X-rays), electron beams and ultraviolet rays, it is not always necessary to introduce monomer for giving a curing site. In crosslinking with high energy rays, since no crosslinking agent such as an organic peroxide is required and thus no step for kneading a crosslinking agent is necessary, it is possible to not only simplify a preparation step but also avoid contamination in a kneading step. Thus crosslinking with high energy rays is suitable particularly for production of various molded articles used for production of semiconductors and required to be highly free from contamination. However in an application where a sealing property at high temperature is demanded, it is advantageous from the viewpoint of physical properties to introduce a curing site and crosslink by using an organic peroxide and crosslinking aid or a crosslinking agent such as bisaminophenol having a functional group reactable with a nitrile group.
The elastomeric segment A can be prepared by iodine transfer polymerization method known as a process for preparing a fluorine-containing elastomer (JP-B-58-4728, JP-A-62-12734).
For example, there is a method of carrying out emulsion polymerization with stirring the above-mentioned perhaloolefin and if necessary, monomer giving a curing site under pressure in water medium substantially under oxygen-free condition in the presence of an iodine compound, preferably a diiodine compound and a radical polymerization initiator.
Represented examples of diiodine compound to be used are, for instance, 1-3-diiodoperfluoropropane, 1,4-diiodoperfluorobutane, 1,3-diiodo-2-chloroperfluoropropane, 1,5-diiodo-2,4-dichloroperfluoropentane, 1,6-diiodoperfluorohexane, 1,8-diiodoperfluorooctane, 1,12-diiodoperfluorododecane, 1,16-diiodoperfluorohexadecane, diiodomethane and 1,2-diiodoethane. Those compounds can be used alone or in combination of two or more thereof. Among them, 1,4-diiodoperfluorobutane is preferred. An amount of the diiodine compound is from 0.01 to 5% by weight on the basis of a total weight of monomers constituting the elastomeric segment A.
When a polymerization temperature exceeds 60xc2x0 C., characteristics under normal condition seem not affected particularly, but compression set tends to be lowered. When less than 40xc2x0 C., in case of single use of persulfate, polymerization speed is low. Also even if a persulfate-added redox type initiator is used, polymerization speed is low and besides a metal ion of a reducing agent remains in the polymer, which makes it impossible to use in application for production of semiconductors.
A radical polymerization initiator which is used for preparing the elastomeric segment A of the present invention may be the same as that which has been used for polymerization of a fluorine-containing elastomer. Examples thereof are organic and inorganic peroxides and azo-compounds. Represented examples of the initiator are persulfates, carbonate peroxides, peroxide esters, and the like. Preferred initiator is ammonium persulfate (APS). APS can be used solely or in combination with a reducing agent such as sulfites. However in many cases since an obtained elastomer is used as a sealing material for semiconductor production apparatuses, etc. in which a high cleanliness is demanded, it is preferable not to use a reducing agent as a source for generating metal ions if possible.
Though a wide range of emulsifying agents can be used for emulsion polymerization, from a point of inhibiting a chain transfer reaction with molecules of the emulsifying agent which occurs during the polymerization, carboxylic acid salts having a fluorocarbon chain or fluoropolyether chain are desirable. An amount of the emulsifying agent is desirably from about 0.05% by weight to 2% by weight, particularly desirably from 0.2 to 1.5% by weight based on added water.
Since the monomer mixture gas used in the present invention is explosive as described in Advances in Chemistry Series, G. H. Kalb et al, 129, 13 (1973), it is necessary to take measures for a polymerization equipment not to cause a sparking. From that point of view, it is preferable that a polymerization pressure is as low as possible.
The polymerization pressure can be changed in a wide range, generally from 0.5 to 5 MPa. The higher the polymerization pressure is, the more a polymerization speed increases. Therefore the polymerization pressure is desirably not less than 0.8 MPa from the viewpoint of increasing productivity.
It is preferable that a number average molecular weight of the so-obtained elastomeric segment A is from 5,000 to 750,000, particularly from 20,000 to 400,000 from the viewpoint of imparting flexibility, elasticity and mechanical properties to the whole fluorine-containing multi-segment polymer obtained and also from the viewpoint of moldability.
In the present invention, an end of the elastomeric segment A is of perhalo type and has an iodine atom which becomes a starting point of block copolymerization of the non-elastomeric segment.
In the present invention, the non-elastomeric segment B is basically not limited if it has a fluorine atom and does not have the above-mentioned elastomeric property. The non-elastomeric segment B may be selected according to characteristics and functions which are intended to be obtained by block-copolymerizing the non-elastomeric segment B. A cystalline polymer chain segment having a crystalline melting point of not less than 150xc2x0 C. is preferred to impart mechanical properties.
Among monomers constituting the non-elastomeric segment B, examples of a fluorine-containing monomer are, for instance, one or two or more of perhaloolefins such as TFE, CTFE, PAVE, HFP, CF2xe2x95x90CF(CF2)pX in which p is an integer of 1 to 10, X is F or Cl, and perfluoro-2-butene; and partly fluorinated olefins such as vinylidene fluoride, vinyl fluoride, trifluoroethylene,
CH2xe2x95x90CX1"Parenopenst"CF2"Parenclosest"qX2
in which X1 and X2 are H or F, q is an integer of 1 to 10, and CH2xe2x95x90C(CF3)2. Also one or two or more of monomers copolymerizable therewith, for example, ethylene, propylene, vinyl chloride, vinyl ethers, vinyl esters of carboxylic acid and acryls can be used as copolymerizable components.
Among them, examples of preferred monomer used as a main component are a single use of fluorine-containing olefin, a combination of fluorine-containing olefins, a combination of ethylene and TFE and a combination of ethylene and CTFE from the viewpoint of chemical resistance and heat resistance. Particularly a single use of perhaloolefin and a combination of perhaloolefins are preferred.
Examples thereof are
(1) VdF/TFE (0 to 100/100 to 0), particularly VdF/TFE (70 to 99/30 to 1), PTFE or PVdF;
(2) ethylene/TFE/HFP (6 to 60/40 to 81/1 to 30), 3,3,3-trifluoropropylene-1,2-trifluoromethyl-3,3,3-trifluoropropylene-1/PAVE (40 to 60/60 to 40);
(3) TFE/CF2xe2x95x90CFxe2x80x94Rf1 (amount exhibiting non-elastomeric property, namely not more than 15% by mole of CF2xe2x95x90CFxe2x80x94Rf1);
(4) VdF/TFE/CTFE (50 to 99/30 to 0/20 to 1);
(5) VdF/TFE/HFP (60 to 99/30 to 0/10 to 1);
(6) ethylene/TFE (30 to 60/70 to 40);
(7) polychlorotrifluoroethylene (PCTFE);
(8) ethylene/CTFE (30 to 60/70 to 40);
and the like. Among them, particularly preferred from the viewpoint of chemical resistance and heat resistance are non-elastomeric copolymers such as PTFE and TFE/CF2xe2x95x90CFxe2x80x94Rf1.
As a monomer constituting the non-elastomeric segment B, the above-mentioned monomer giving a curing site for various vulcanizations may be introduced in an amount of not more than 5% by mole, preferably not more than 2% by mole, more preferably not more than 1% by mole.
Block copolymerization of the non-elastomeric segment B can be carried out subsequently to the emulsion polymerization of the elastomeric segment A by changing a monomer to one for the non-elastomeric segment B.
A number average molecular weight of the non-elastomeric segment B can be adjusted in a wide range of from 1,000 to 1,200,000, preferably from 3,000 to 400,000.
An important feature of the present invention is that the non-elastomeric segment B can be securely block-copolymerized with the elastomeric segment A and that a molecular weight (degree of polymerization) of the non-elastomeric segment B can be increased. As mentioned above, this can be achieved by making the elastomeric segment A have perhaloolefin units of not less than 90% by mole, particularly not less than 95% by mole as a recurring unit.
The thus obtained fluorine-containing multi-segment polymer mainly comprises polymer molecules (B-A-B) in which the non-elastomeric segments B are bonded to both sides of the elastomeric segment A and polymer molecules (A-B) in which the non-elastomeric segment B is bonded to one side of the elastomeric segment A. An amount of polymer molecules (C) which comprises only the elastomeric segment A without being bonded to the non-elastomeric segment B is not more than 35% by weight, particularly not more than 10% by weight based on a total amount of the segment A and polymer (C) in the fluorine-containing multi-segment polymer. Elution of the polymer molecule (C) is caused by, for example, a fluorine-containing organic solvent even after vulcanization, which causes not only deterioration of quality of molded article but also contamination. Therefore an amount thereof is preferably as small as possible, desirably not more than 5% by weight, particularly zero substantially.
In the present invention, a proportion of the elastomeric segment A to the non-elastomeric segment B in the fluorine-containing multi-segment polymer may be selected in the above-mentioned range of molecular weight. The proportion A/B in weight ratio is, for example, to 99/90 to 1, particularly preferably 60 to 95/40 to 5.
The process for preparing the fluorine-containing multi-segment polymer of the present invention as a block polymer is as explained above. Also a graft polymer prepared through a preparation process disclosed in JP-A-62-34324 can be used.
The molding material of the present invention comprises the above-mentioned fluorine-containing multi-segment polymer, and known additives can be used optionally depending on application, crosslinking method and required physical properties (mechanical properties, electrical properties, appearance).
Also when crosslinking points are provided by introducing curing sites into the the elastomeric segment A and/or the non-elastomeric segment B, vulcanization (crosslinking) can be carried out by peroxide vulcanization with known organic peroxides, polyol vulcanization with known polyols, polyamine vulcanization with known polyamine compounds, triazine vulcanization with known organotin catalysts or vulcanization with a crosslinking agent having a functional group reactable with a nitrile group.
In case of peroxide vulcanization, it is preferable to use a crosslinkable molding composition comprising the above-mentioned fluorine-containing multi-segment polymer having a curing site, organic peroxide and crosslinking aid.
Organic peroxide to be used may be any of known organic peroxides which generate peroxy radicals under vulcanization temperature condition. Examples of the preferred organic peroxide are di-t-butyl peroxide, dicumyl peroxide, 2,5-dimethyl-2,5-di(benzoylperoxy) hexane, 2,5-dimethyl-2,5-di(t-butylperoxy) hexane, 1,1-bis(t-butylperoxy)-3,5,5-trimethylcyclohexane, 2,5-dimethylhexane-2,5-dihydroxy peroxide, t-butylcumyl peroxide, xcex1,xcex1xe2x80x2-bis(t-butylperoxy)-p-diisopropylbenzene, 2,5-dimethyl-2,5-di(t-butylperoxy)hexyne-3, benzoyl peroxide, t-butylperoxybenzene, t-butylperoxy maleate, t-butylperoxyisopropyl carbonate, and the like.
A content of the organic peroxide is usually from 0.05 to 10 parts, preferably from 1 to 5 parts on the basis of 100 parts of fluorine-containing multi-segment polymer.
When the content of organic peroxide is less than 0.05 part, the fluorine-containing multi-segment polymer is not crosslinked sufficiently. On the contrary, when more than 10 parts, physical properties of a vulcanizate are lowered.
In such peroxide vulcanization, a crosslinking aid such as a polyfunctional co-crosslinking agent can be used. The usable polyfunctional co-crosslinking agents are those used together with an organic peroxide in peroxide vulcanization of a fluorine-containing elastomer. Examples thereof are, for instance, bisolefins represented by triallyl cyanurate, trimethallyl isocyanurate, triallyl isocyanurate, triallyl formal, triallyl phosphate, triallyl trimellitate, N,Nxe2x80x2-m-phenylenebismaleimide, dipropargyl terephthalate, diallyl phthalate, tetraallyl terephthalamide, tris(diallylamine)-S-triazine, triallyl phosphite, N,N-diallylacrylamide and 1,6-divinyldodecafluorohexane.
Also there are a fluorine-containing triallyl isocyanurate which is obtained by replacing a part of hydrogen atoms in three allyl groups of triallyl isocyanurate with fluorine atoms having higher heat resistance, and the like (cf. U.S. Pat. No. 4,320,216, WO98/00407, Klenovic h, S. V. et al, Zh. Prikl, Khim. (Leningrad) (1987, 60(3), 656-8)).
A content of a crosslinking aid is usually from 0.1 to 10 parts, preferably from 0.5 to 5 parts on the basis of 100 parts of fluorine-containing multi-segment polymer.
When the content of the crosslinking aid is less than 0.1 part, the fluorine-containing multi-segment polymer is not vulcanized sufficiently. On the contrary, when more than 10 parts, elongation of a vulcanizate is lowered.
When vulcanizing a fluorine-containing multi-segment polymer having a nitrile group as a curing site, it is preferable to use a crosslinkable molding composition comprising a fluorine-containing multi-segment polymer having a nitrile group and a crosslinking agent having a functional group such as bisaminophenol reactable with the nitrile group.
Examples of the crosslinking agent having a functional group reactable with a nitrile group are known bisaminophenol compounds, tetraamine compounds, bisaminothiophenol compounds, bisamidrazone compounds, bisamidoxime compounds (cf. JP-A-59-109546, JP-A-8-120144, JP-A-8-104789, JP-A-8-119926, JP-A-8-217742, JP-A-9-31283, JP-A-9-31284), and the like.
In the molding material and crosslinkable molding composition of the present invention, particularly in the fields where high purity and freedom from contamination are not demanded, usual additives which are added to a fluorine-containing elastomer composition can be blended as case demand, for example, a filler, processing aid, plasticizer, coloring agent, and the like. At least one usual vulcanizing agent or vulcanizing accelerator which differs from those mentioned above may be added. Also a known fluorine-containing rubber may be mixed in the range not lowering an effect of the present invention.
The molding material and crosslinkable molding composition of the present invention can be prepared by mixing each of the above-mentioned components by using conventional rubber processing machine, for example, open roll, banbury mixer, kneader, etc. and besides, can be prepared by a method using a closed mixer and a coagulation method through emulsion mixing.
In order to obtain a pre-molded article from the above-mentioned molding material and crosslinkable molding composition, a usual method may be employed. There can be employed known methods such as a method of heating and compressing in a die, a method of feeding under pressure in a heated die and a method of extruding. In case of extruded products such as hose and wire, since they can maintain their forms after extrusion, pre-molded articles obtained by extrusion without using a crosslinking agent can be used as they are. Of course it is possible to use pre-molded articles subjected to crosslinking by heating with steam by using a crosslinking agent. Also in case of molded articles such as O-ring which are difficult to maintain shapes thereof after releasing when not subjected to crosslinking, it is possible to use a pre-molded article previously subjected to crosslinking by using a crosslinking agent.
In the present invention, peroxide vulcanization can be carried out under conventional vulcanization conditions of a fluorine-containing rubber. For example, a vulcanized rubber can be obtained by putting in a metal die, press-vulcanizing by holding under pressure at 120xc2x0 to 200xc2x0 C. for 1 to 60 minutes and then vulcanizing in an oven by holding at 120xc2x0 to 320xc2x0 C. for 0 to 48 hours.
In the present invention, vulcanization with a crosslinking agent such as bisaminophenol can be carried out under conventional vulcanization conditions of a fluorine-containing rubber. For example, a vulcanized rubber can be obtained by putting in a metal die, press-vulcanizing by holding under pressure at 120xc2x0 to 200xc2x0 C. for 1 to 60 minutes and then vulcanizing in an oven by holding at 120xc2x0 to 320xc2x0 C. for 0 to 48 hours.
In case of applications such as semiconductor-related production apparatuses where freedom from contamination is strongly demanded, it is preferable to carry out crosslinking with high energy rays without adding a crosslinking agent. Examples of such rays are radiation such as xcex1-ray, xcex2-ray, xcex3-ray and X-ray, electron beams and ultraviolet rays.
With respect to high energy rays emitted to a pre-molded article, for example, in case of electron beams, an amount of emitting rays is preferably from 5 to 500 kGy, more preferably from 10 to 300 kGy. When less than 5 kGy, improvement in mechanical strength by emitting radiation is insufficient, and when more than 500 kGy, degradation of polymer advances and bonding between molecules is partly cut, which results in lowering of mechanical strength of a molded article. Also in order to improve mechanical strength, emission is preferably not less than 500 kGy/hr, more preferably not less than 1,000 kGy/hr.
In case of use as a molding material for various molded articles for semiconductor production apparatuses, for example, a sealing material, characteristics for resisting under strict conditions against strong acids such as hydrofluoric acid, ammonium fluoride, hydrochloric acid and sulfuric acid; alkalis such as ammonia, sodium hydroxide and amines; various plasmas such as oxygen, neon and CF4; and the like are demanded. In order to meet such demand, the molding material of the present invention comprising the following components may be used.
(1-a) Elastomeric Segment A
Copolymer comprising 45 to 90% by mole of tetrafluoroethylene, 10 to 50% by mole of perfluoro(alkyl vinyl ether) and 0 to 5% by mole of monomer giving a curing site and having iodine atom
Molecular weight: 20,000 to 400,000
(1-b) Non-elastomeric Segment B
Preferred are tetrafluoroethylene homopolymer, a copolymer comprising 90 to 99.99% by mole of tetrafluoroethylene and 0.01 to 10% by mole of perfluoro(alkyl vinyl ether), a copolymer comprising 85 to 99.99% by mole of tetrafluoroethylene and 0.01 to 15% by mole of hexafluoropropylene, and the like.
Molecular weight: 1,000 to 400,000
Basically it is preferable not to use additives. Only in necessary cases for reinforcement and lowering of electrostatic charge depending on purpose and parts, a smaller amount of carbon black, titanium oxide, silicon oxide, fluorine-containing resin powder, etc. may be added.
Though sufficient strength can be obtained even if vulcanization is not carried out, when enhancing mechanical properties by vulcanization, known vulcanization method can be employed. However if possible, a vulcanization method without using metal, metal compound and metal ion is preferred. Concretely preferred are peroxide vulcanization, bisaminophenol vulcanization and vulcanization with high energy ray such as radiation, electron beam or ultraviolet ray.
Known injection molding, extrusion molding and compression molding can be applied.
The fluorine-containing multi-segment polymer of the present invention is excellent in properties as an elastomer such as flexibility, elasticity and sealing property and in properties as a crystalline resin such as mechanical strength, abrasion resistance and heat resistance. Further since the both segments are chemically bonded to each other, the polymer is excellent in cleanliness and transparency.
The molding material and composition of the present invention are useful as materials for various molded articles in the fields shown in Tables 1 to 3 making the best use of the above-mentioned characteristics.
Particularly the sealing material of the present invention can be used built in the following semiconductor production apparatuses.
Dry etching equipment
Plasma etching device
Reactive ion etching device
Reactive ion beam etching device
Sputter etching device
Ion beam etching device
Wet etching equipment
Ashing equipment
Dry etching cleaning equipment
UV/O3 cleaning device
Ion beam cleaning device
Laser beam cleaning device
Plasma cleaning device
Gas etching cleaning device
Extraction cleaning equipment
Soxhlet extracting cleaning device
High temperature high pressure extracting cleaning device
Micro wave extracting cleaning device
Supercritical extracting cleaning device
Stepper
Coater developer
CMP equipment
CVD equipment
Sputtering equipment
Oxidation diffusion equipment
Ion implantation equipment